Pathfinder Reservoir
Natrona County, WyomingView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Public access
- Limited data
Pathfinder Reservoir in Natrona County, Wyoming is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 10 µg/L.
- Phosphorus
- 10 µg/L
- Trend
- → Stable
- Public access
- Yes
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Watch Pathfinder Reservoir’s letter
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Why Pathfinder Reservoir has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Pathfinder Reservoir, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus, but not water clarity and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by Wyoming DEQ and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Pathfinder Reservoir is a lake in Natrona County, Wyoming. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Wyoming DEQ, last sampled 2015-09-23. Grade methodology: LakeQuality methodology.
What Pathfinder Reservoir is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Pathfinder Reservoir
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Phosphorus 10 µg/L. TSI 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 10 µg/L | Not graded |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Recreation & Access
- Pathfinder ReservoirPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Pathfinder Reservoir
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | → Stable | +0.23 µg/L/yr | 5 |
Reservoir Info (USACE NID)
Pathfinder Reservoir is a man-made reservoir impounded by the Pathfinder Dike (completed 1911), built primarily for fish and wildlife pond on the North Platte River Offstream; earth-type dam, 38 ft tall and 1,650 ft long.
- Normal storage
- 1,016,500 ac-ft
- Max storage
- 1,016,500 ac-ft
- Hazard class
- High
- Owner
- BUREAU OF RECLAMATION
All listed purposes: Fish and Wildlife Pond;Irrigation;Hydroelectric;Water Supply.
Source: USACE National Inventory of Dams, NID ID WY01295 · Operator website
Graded lakes near Pathfinder Reservoir
Pathfinder Reservoir has no grade, but these lakes within a short drive do.
Nearby Lakes in Natrona County
Frequently asked questions about Pathfinder Reservoir
Where is Pathfinder Reservoir?
- Pathfinder Reservoir is a lake in Natrona County, Wyoming. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Pathfinder Reservoir?
- Pathfinder Reservoir in Natrona County, Wyoming is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 10 µg/L.
Is Pathfinder Reservoir safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Pathfinder Reservoir?
- Pathfinder Reservoir has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Pathfinder Reservoir. Public access is listed as yes.
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Where this data comes from
1 measurement from 1 monitoring station, 2015. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- State of Wyoming Department of Environmental Quality Watershed Program
WYDEQ_WATERSHED1 sample · 2015
Analytical methods
- Total Phosphorus After Block Digestion
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Named boat-access points from the USGS National Boat Ramps inventory